1. Field of the Invention
The present invention relates to the field of roofing and siding materials, and in particular, to interlocking decorative roofing and siding panels.
2. Description of Prior Art
The present inventor has manufactured various types of simulated roofing panels and roofing panel systems utilizing thermoplastic sheet and vacuum forming processes for a number of years. Such panels typically have simulated either Spanish tile or wood shake roofing, though the general materials and techniques may be used, and in many cases have been used, to simulate other roof coverings such as Chinese tile or coverings having an aesthetic appearance unlike that of any of the historically conventional roofing materials. By way of example, the present inventor has manufactured simulated Spanish tile non-interlocking panels in accordance with U.S. Pat. No. 3,485,002. The present inventor has also manufactured simulated shake panels, particularly of a non-interlocking panel design, having an ornamental appearance generally in accordance with U.S. Pat. No. 4,343,126. Non-interlocking panels of this general type are generally used for mansards and indoor decorative purposes, but are not frequently used for roof area coverage because of the fact that they require exposed fasteners.
Interlocking shake and tile panels are disclosed in U.S. Pat. Nos. 4,343,126 and 4,251,967, respectively. In the case of the first of these patents, the top of the nailing flange of each panel is doubled back onto the lower part of the nailing flange to provide a downward facing slot or hook to engage the front edge of the panel in the next higher course, which front edge is bent under the panel for this purpose. The nailing flange is of course still used to fasten the rear of each panel to a roof by nailing or stapling through the double thickness flange, with the front of each panel being retained by the engagement of the front lip with the hook formed by the nailing flange. While this system works well, manufacture of the panel requires that the bending of the front lip under the panel and the bending of the nailing flange into the downward facing U-shape generally be done as secondary operations to the vacuum forming operation, particularly after the trimming subsequent to vacuum forming. Further, while installation is much faster than with conventional shake, care must be taken and some delay is encountered in obtaining and being sure of proper engagement of vertically adjacent panels on a roof.
The foregoing problems are overcome by the interlocking panels of U.S. Pat. No 4,251,967. In particular, that patent discloses an interlocker comprising a slot or channel typically running all the way across the lower part of the back of the decorative element in a simulated tile or shake panel so as to form a discontinuous slot across the width of the back of the panel. The front of each panel has a cooperatively disposed lip-like region which engages the channel at the back of a panel so that the panels quickly slip together during installation to minimize installation time. Further, by using an appropriate vacuum forming mold, the vacuum forming of the entire panel including the interlockers may be done in a single step, thereby minimizing secondary operations in the manufacturing process. However, the vacuum formed sheet thins out substantially in the corner regions of the intersection of the slot at the back of the panel and the edges of the decorative elements, particularly in the outward projecting corners thereof at the rear of the decorative element. This effect may be readily minimized with simulated tile panels if the panels overlap each other, as illustrated with the primary embodiment of that patent, by providing a generous radius on the corresponding corners of the decorative elements. Similar techniques may also used in the corresponding regions of simulated shake panels, though the extent of the rounding of the corners which can be used is perhaps more limited than with the tile panels if the rounding is not to effect the visual appearance of the installed roof. Obviously such thinning during the vacuum forming process would be non-existent if the product were injection molded rather than vacuum formed. Even in such case, the extension of the discontinuous slot entirely across the back of a decorative element may still effect the visual appearance of the finished roof. The slot shown in that patent cannot be terminated short of the edges of each decorative element, however, as to do so would create a water trap, with freezing of the trapped water possibly cracking or loosening the panels.